Boom angle indicator for cranes



Nov. 27, 1956 c. M. COOPER 2,772,411

' BOOM ANGLE INDICATOR FOR CRANES Filed Oct. 25, 1954 fl/a m. 6/14 M600/ 4 08 United States Patent ice BOOM ANGLE INDICATOR FOR CRANES CarlM. Cooper, Compton, Calif., assignor of forty percent to S. Fishfader,Los Angeles, Calif.

Application October 25, 1954, Serial No. 464,233

3 Claims. (Cl. 340-282) This invention relates to a device whereby theangle or position of the boom of a crane will be indicated to theoperator of the crane, this indicator being within the cab so that theoperator will at all times be apprised of the exact position of thecrane boom.

An object of my invention is to provide a boom position indicator forcranes in which the pendulum on the boom actuates a potentiometer, thepotentiometer being wired to an ammeter or voltmeter situated in the cabof the crane.

Another object of my invention is to provide a novel boom indicator forcranes, in which the ammeter or voltmeter is also connected to a mercuryswitch which indicates the tilt or angle of the cab to serve as awarning if the cab or crane is tilting to a dangerous degree, due to anexcessive load on the boom.

Another object of my invention is to provide a novel boom angleindicator of the character stated, in which the pendulum is mountedwithin a housing and is damped in a suitable liquid to prevent excessiveoscillation of the pendulum.

Other objects, advantages and features of invention may appear from theaccompanying drawing, the subjoined detailed description and theappended claims.

In the drawing:

Figure 1 is a side elevation of a crane with my boom indicatingmechanism mounted thereon.

Figure 2 is a wiring diagram of my boom indicator.

Figure 3 is a side elevation of the boom angle indicator.

Figure 4 is a front elevation of the same with the cover plate removed.

Figure 5 is a sectional view taken on line 5-5 of Figure 4.

Referring more particularly to the drawing, the numeral 1 indicates thecab of a crane and 2 the boom of that crane. In a boom type crane,particularly those of the portable types, it is possible to tip thecrane over by attempting to lift too great a load, or if the boom is atan incorrect angle a lesser load on the boom will also tip the crane,and for these reasons it is desirable that the operator be apprised ofthe exact angle of the boom without having to observe the boom visuallyand estimate the angle and Whether that angle is safe. With my inventiona visual means is provided Within the cab 1 of the crane so that theoperator can observe a finger or needle of an instrument, this needleindicating in degrees the angle of the boom. A housing 3, preferablycylindrical in shape, is mounted on the boom 2 by means of an arm 4which projects downwardly from the housing and is fixedly attached to aC-clamp 5. The C-clamp 5 attaches to a suitable member of the boom 2. Ahorizontal shaft 6 is journaled in the housing 3 and projects into thetube 7, projecting from the rear of the housing 3. A resistance orpotentiometer 3 is mounted Within the tube 7 and a finger 9 on the shaft6 moves over the potentiometer as the shaft 6 is rotated. A pendulum 1Gis suspended from the shaft 6 and is positioned within the housing 3. Itwill be evident that as the boom 2 moves upwardly 2,772,411 PatentedNov. 27, 1956 and downwardly in an are, that the pendulum 10 will movewithin the housing 3, thus rotating the shaft 6 and thereby moving thecontact finger 9 over the potentiometer 8. The movement of the pendulum10 is clamped by the liquid 11 which partly fills the housing 3. Thehousing 3 and the pendulum 10 therein, can be so positioned on the arm 2that the finger 9 will be at the zero position of the potentiometer 8when the boom 2 is in its extreme raised position. As the boom 2 islowered, the finger 9 will move over the potentiometer 8, thus varyingthe resistance in the electrical circuit, to be further described, andactuating a voltmeter or ammeter, the needle of which moves over a chartcalibrated in degrees. The voltmeter 12 is mounted in the cab 1 of thecrane and is so positioned that the operator can easily see the dial 13which is calibrated in degrees, as previously stated. The finger 14 ofthe voltmeter moves over the dial 13, as will be evident, depending uponthe position of the finger 9 on the potentiometer 8.

The wiring diagram is as follows: A source of power, preferably abattery 15, supplies power to the leads 16 and 17 extending therefrom. Aswitch. 18 may be included in the circuit, if desired. The lead 16extends to one end of the potentiometer 3 and the lead 17 extends to theother end of that potentiometer. A push button switch 19 has contacts 20and 21 and the contact 20 is connected by lead 22 to the shaft 6, or tothe finger 9 which sweeps the potentiometer 8. The contact 21 isconnected by lead 23 to a rheostat 24. This rheostat is the usualadjusting rheostat of a voltmeter whereby the hand 14 can be adjusted toa zero position. A second set of contacts 25-26 of the switch 19 areconnected as follows: The contact 25 is connected to the lead 17.Similarly, the contact 26 is connected to the lead 23, as shown. Thus inone position the switch 19 engages the contacts 20-21, and in thisposition the potentiometer 3 through the position of the finger 9thereof will actuate the voltmeter 12, causing the hand 14- thereof tomove to a position corresponding to the position of the finger 9, butsince the dial 13 is calibrated in degrees the operator will be able toread the angle of the boom 2 in degrees and determine if that angle isafe or unsafe. When the switch 19 engages the contacts 25-26, currentflows to the rheostat 24 for the purpose of adjusting the hand 14 of thevoltmeter in the usual manner. A mercury switch 27 includes severalcontacts 28, 29 and 30. The drop of mercury in the switch will move toengage these contacts as the switch is tilted. The switch 27 is mountedeither upon or adjacent to the voltmeter 12 and thus as the cab 1 mighttilt the switch 27 would be actuated to give a warning. The contact 28of the switch 27 is connected to the lead 16 by the wire 33. A buzzer32, or other audible Warning, is connected by lead 33 to the contact 29;the other side of the buzzer being connected by lead 34 to the main line17. A warning light 35 may also be included in the circuit and thislight is connected by lead 36 to the lead 31 and the contact 39, and bythe lead 37 to one end of the potentiometer d or to the lead 17, whichin this instance is the same thing.

In operation as the boom 2 raises and lowers on its pivot the pendulum10 will swing in the housing 3, thus moving the finger 9 over thepotentiometer 8. The voltage supplicd to the voltmeter 12 is thusvaried, causing the hand 14' of the voltmeter to move over the dial 13,indicating in degrees the position of the boom 2. Any excessive tiltingof the cam 1 of the crane causes the mercury switch 27 to engagecontacts 29 or 30, thus actuating the buzzer 32 or the light 35. Thependulum 10 is prevented from violently swinging back and forth withinthe housing 3 by the liquid (such as oil) within the housing and inwhich the pendulum moves.

Having described my invention, I claim:

1. A boom angle indicator for cranes comprising a housing, attachingmeans on the housing to secure said housing to the boom, a pendulumpivotally mounted in the housing, a variable resistance, means operableby the pendulum to vary the resistance, a galvanometer, and electricalleads extending from said resistance to the galvanometer, saidgalvanometer being calibrated in degrees, a tilt switch mounted adjacentthe galvanometer, a warning means, and electrical leads extending fromthe tilt switch to the warning means.

,2. A boom angle indicator for cranes comprising a housing, attachingmeans on the housing to secure said housing to the boom, a shaftextending into the housing, a pendulum mounted on the shaft andpositioned within the housing, a variable resistance mounted on thehousing, said shaft extending to the variable resistance, a finger onthe shaft adapted to sweep over the variable resistance, a galvanometer,and electrical leads extending from said resistance to the galvanometer,said galvanometer being calibrated in degrees, a tilt switch mountedadjacent the galvanometer to indicate excessive tilting of saidgalvanometer, a warning means, and electrical leads extending from thetilt switch to the warning means.

3. A boom angle indicator for cranes comprising a housing, attachingmeans on the housing to secure said housing to the boom, a shaftextending into the housing, a pendulum mounted on the shaft andpositioned within the housing, a damping liquid in the housing in whichthe pendulum is immersed, a variable resistance mounted on the housing,said shaft extending to the variable re sistance, a finger on the shaftadapted to sweep over the variable resistance, a vgalvanorneter, andelectrical leads extending from said resistance to the galvanometer,said galvanometer being calibrated in degrees, a tilt switch mountedadjacent the galvanometer to indicate excessive tilting of saidgalvanometer, a warning means, and electrical leads extending from thetilt switch to the warning means.

References Cited in the file of this patent UNITED, STATES PATENTS561,431 Pfatischer June 2, 1896 2,330,060 Kuehni Sept. 21, 19432,346,066 Conrad Apr. 4, 1944 2,418,576 Conrad Apr. 8, 1947 2,448,597Jolley et a1 Sept. 7, 1948 2,474,610 Wunsch June 28, 1949

